SME finance is the funding of small and medium-sized enterprises, and represents a major function of the general business finance market in which capital for different types of firms is supplied, acquired, and costed or priced. Capital is supplied through the business finance market in the form of bank loans and overdrafts; leasing and hire-purchase arrangements; equity/corporate bond issues; venture capital or private equity; asset-based finance such as factoring and invoice discounting, and government funding in the form of grants or loans.

The economic and banking importance of the small and medium enterprise (SME) sector is well recognized in academic and policy literature. It is also acknowledged that these actors in the economy may be under-served, especially in terms of finance. This has led to significant debate on the best methods to serve this sector.

Although there have been numerous schemes and programmes in different economic environments, there are a number of distinctive recurring approaches to SME finance.

A substantial portion of the SME sector may not have the security required for conventional collateral based bank lending, nor high enough returns to attract formal venture capitalists and other risk investors. In addition, markets may be characterized by deficient information (limiting the effectiveness of financial statement-based lending and credit scoring). This has led to claims of an "SME finance gap" or Nano gap– particularly in emerging economies. At a workshop hosted by The Network for Governance, Entrepreneurship & Development (GE&D) in Geneva in July 2008, SMEs that fall into this category have been defined as Small Growing Businesses (SGBs).

There have been at least two distinctive approaches to try to overcome the so-called SME finance gap.

The first has been to broaden the collateral based approach by encouraging bank lenders to finance SMEs with insufficient collateral. This might be done through an external party providing the collateral or guarantees required. Unfortunately, such schemes are counter to basic free market principles, and they tend to be unsustainable. This sector is increasingly called the Meso-finance sector.

However, there are no evidence of any significant structural barriers to the supply of bank or private equity finance to suitable SME applicants on mutually satisfactory terms and conditions in Britain. The main obstacles to funding here appear to be on the demand rather than the supply side of the business finance market. This is mainly in the form of:

Thus, the second approach has been to broaden the viability based approach. Since the viability based approach is concerned with the business itself, the aim has been to provide better general business development assistance to reduce risk and increase returns. This often entails a detailed review and assistance with the business plan.